Cause –
Why this is an issue for the exploring biker is
that it is agreed that the cause of AMS is rapid
ascent and few people go up a mountain pass
quicker than a biker! The reason being is that
the air is thinner the higher you go, you get the
same percentage of gases, so 21% of the air is
still oxygen but there is less oxygen in that
volume ... get it? Right – in low altitude the air
is packed tighter, so you get more stuff in say 1
sq metre. As you go up the pressure is lower so
the stuff spreads out, you get the same ratio in
1 sq metre 21% but less of the volume. That’s
how it was explained to me after I asked for
the fourth time.
Right James, last time of explaining this – At
low altitude you get say 1000 bits of stuff in a
shoe box, 21% of that stuff is oxygen so James
gets 210 bits of oxygen per box, get it? I
nodded and thought about taking a shoe box
on the next ride just in case. At high altitude
the shoe box only has 100 bits of stuff but still
gets you 21% oxygen = 21 bits of oxygen!
Ohhhhhhh ok I got it, will take the shoe box in
the pannier.
Another factor is that old time favourite of
bikers, dehydration. Being exposed to the
elements is all part of the fun of riding, as the
sun beats down the air rushes over your skin
it’s fantastic. We know this causes vapour loss
but at high altitude just breathing causes
higher vapour loss from your lungs! So keep
those fluids up.
Physical activity is another big factor of AMS
and throwing around your machine on those
yummy inclined switchbacks has you working
rather hard for your fun. Make that a gravel
mountain pass and you’re doubling your
output... along with the fun in my opinion!
Fun aside this can get very serious and can be
fatal at VERY high altitude. So let’s have a look
at what it is, how to spot it and what we can do
about it.